Windows 10 for the second straight month surged in user share as the drive toward the deadline for its Windows 7 predecessor entered its final five months.

According to analytics company Net Applications, Windows 10's share of all personal computers jumped 2.1 percentage points - the second consecutive month of two or more points - to close August at 51%. It was the first time Windows 10 accounted for a majority of all personal computer operating systems. Windows 10's part of Windows PCs, meanwhile, climbed to 58%, putting the OS on track to power two-thirds of all Windows machines by the time Microsoft rolls out its next major feature upgrade next March.

(The second number - the percentage of Windows PCs - is larger than the first because Windows does not power every PC; in August, Windows ran 87.9% of the world's machines. All but a Lilliputian fraction of the rest ran macOS, Linux or Chrome OS.)

As Windows 10's share jumped, Windows 7 dropped, albeit at not the same rate. Windows 7's share fell by 1.5 percentage points to 30.3% of all personal computers and 34.5% of those running Windows. The monthly decline was less than half of July's but still the fifth-largest over the past 12 months. August was also the sixth straight month of decline for the aged operating system, which is to be retired from public support on Jan. 14, 2020.

Also on the downswing, and in a major way, was the duo of Windows 8 and Windows 8.1. (The former is officially unsupported by Microsoft, yet approximately seven-tenths of one percent of all Windows PCs still run that OS.) Together, they shed 1.1 percentage points of share, the largest amount since December 2016 when Windows 8.1 was near the tail of its post-Windows 10-debut downturn. Now at just 4.8% of all PC operating system and 5.5% of those running Windows, the 8/8.1 twosome are slowly, very slowly - like the remnants of Windows XP - vanishing. Unlike most Windows editions, however, these will be nearly invisible by the time their support expires in January 2023.

Less for Windows 7 means more for Windows 10

The continued exodus from Windows 7 and more importantly, the accumulation of share under Windows 10's column, puts the migration's end game in a different light. Where earlier forecasts pegged Windows 7 at-retirement remainder as high as the upper 30s, the numbers are now much more in line with historical trends.

Computerworld's latest forecast - based on the operating system's 12-month average change - now has Windows 7 down to 29.8% at the end of January, nearly a point lower than the prediction made the month before. That shows the impact of the large August decline.

Meanwhile, Windows 10 should account for approximately 64% of all Windows installations when the older OS drops off support, an increase of two points from the month-ago forecast. A year later - January 2021 - Windows 7 and Windows 10 should be at 18% and 79%, respectively, two to three points different than the projection generated from July's data.

The 29.8% currently forecast as Windows 7's share at support expiration is very close to the 29% of all Windows PCs still running Windows XP when that OS left support. Until recently, comparisons between Windows XP's actual decline and Windows 7's predicted descent always portrayed the latter as a loafer and laggard; the data indicated that users were more reluctant to give up Windows 7 than they had XP.

For the moment, that's not be the case.

Microsoft could accelerate the Windows 7-to-Windows 10 movement if it put its money where its mouth is. "If you continue to use Windows 7 after support has ended, your PC will still work, but it will become more vulnerable to security risks and viruses," the company contended in an end-of-support FAQ.

A last minute repeat of the year-long free upgrade offer for Windows 7 Home and Windows 7 Professional systems would go a long ways toward reducing the number of PCs likely to be "more vulnerable to security risks." Although such a move is unlikely - at the least it would impact sales of new Windows 10 Home and Windows 10 Pro - it would not be any more inconceivable than was the 2015-2016 offer.

The 12-month average increase of Windows 10 during the free offer was 1.7 percentage points, according to Net Applications. If Microsoft offered free upgrades immediately and if the effect were similar to the original, the January 2020 user share of Windows 10 would be about 68%, or four points higher than the current forecast. Windows 7 would be approximately four points lower, or around 26%, when it falls off the support list.

What does the difference between 30% and 26% for Windows 7 represent? About 60 million fewer PCs "vulnerable to security risks."